Rockwool 'all wrapped up' for renewable energy

Stonewool insulation from Rockwool is playing a vital and sustainable role in an innovative GBP30 million upgrade to Wessex Water's Avonmouth Waste Water Treatment Works.

Stonewool insulation from Rockwool is playing a vital and sustainable role in an innovative GBP30 million upgrade to Wessex Water's Avonmouth Waste Water Treatment Works which will be used to generate renewable energy as well as improve sewage treatment for the area.

Rockwool RWA45 Stonewool insulation met Wessex Water's specification to maintain an optimum temperature in sludge digester tanks boosting the plants methane production and powering a pioneering gas generation plant, used for electricity generation.

Rockwool Stonewool also met the need for an insulation product which could be cut easily to shape and flexible enough to be fitted to the curved tanks.

John Ford, Project Supervisor at Wessex Water, explains: "A constant 40degC must be maintained as the digested sludge moves successively through six tanks, before discharging to the mesophilic digester.

The correct temperature is essential for efficient digestion and gas production".

The sludge digester is part of the 3-year Bristol Advanced Sludge Scheme, which aims to reduce the volume of sludge disposed to as part of the EU Urban Waste Water Treatment Directive and increase the volume of off-gas for power generation.

The new tanks will help produce an estimated GBP50,000 worth (70,000m3) of additional methane per week from the treatment plant for electricity generation.

The methane feeds the five 1.1MW gas engine dual fuel generators which provide electricity to the WWTW and heat the digesters, currently the plant produces methane equivalent to GBP800,000 worth of green energy per annum.

Rockwool Stonewool is manufactured using igneous volcanic rock, an abundantly-available resource which in its lifetime can save 100s of times the greenhouse gases generated during its production.

Sustainable manufacturing ensures that 50% of Rockwool by weight is made from recycled materials.

Rockwool Stonewool is also critical to the mesophilic sludge digestion process which is a highly energy efficient and 'green' method of anaerobic sludge treatment, prior to its disposal.

John Ford explains: "The glass-lined steel tanks are insulated with 75mm of Rockwool RWA45 Stonewool insulation slabs, which are curved to fit.

The installation is protected by profiled steel sheeting, cut to shape and sealed.

"Sales Director Andrew Peace of Kirk Liquid Management Solutions who installed the six 13 metre high by 8 metre diameter digester tanks complete with insulation and cladding, added: "The cylindrical tanks have a relatively complex geometry, which is more difficult to insulate effectively.

Rockwool Stonewool insulation is the best product in the industry for tank cladding and has an excellent thermal performance and sustainability record.

"After consultation with Rockwool's Technical Department, we decided on the flexible RWA45 panels were used on the tank walls so as to take up the curvature yet ensure secure jointing.".

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